The Pentagon is planning to expand its use of special operations troops, including those that operate covertly in tandem with the CIA's paramilitary force, officials and private experts say.

Special operations forces played a critical role in toppling the Taliban regime in Afghanistan last fall and they almost surely would figure prominently in the earliest stages of a U.S. military action in Iraq, coordinating with local forces opposed to Saddam Hussein and hunting for Scud missile launchers.

Defense Secretary Donald H. Rumsfeld believes the military needs to improve its ability to find and track terrorists around the globe and to take decisive action against them. His moves toward that goal have caused some friction with the CIA and led to concern among some that the Pentagon's civilian leaders will only gather and act on those pieces of intelligence that they want to hear and deliver to the Bush White House. Officially, the Pentagon does not discuss its covert capabilities, but indications of Rumsfeld's interest in this shadowy area are apparent in a recent study by an advisory group.

The study called for the Pentagon and CIA to develop a new capability to "evoke responses" from terrorist groups so they can be attacked pre-emptively. Covert action, psychological operations, computer attacks, special operations forces and "deception operations" would be combined in that role.

Michael Vickers, a former Special Forces soldier and one-time CIA officer, said the evolving nature of the war on terrorism makes it likely that covert military operators will be called on more often in the months ahead. Having successfully chased the al-Qaida from Afghanistan - their main operating base - the United States and its coalition partners may need more unconventional forces to chase down individual fugitives elsewhere.

"This is basically a growth industry," said Vickers, now an analyst at the Center for Strategic and Budgetary Assessments.

The CIA missile strike that killed a suspected al-Qaida leader in Yemen this week is stark evidence that the methods used to target terrorists are changing. It was the kind of pre-emptive action outside a traditional war zone that Rumsfeld wants the military to take.

Rumsfeld is considering adding billions of dollars to the $5 billion budget of the Special Operations Command, the Florida-based headquarters that has responsibility for all of the military's special operations forces - the Army's Rangers and Green Berets, the Navy's Seals and the Air Force's special operations commandos. He also may approve increases in the numbers of such troops, now totaling 45,000, including reservists.

The defense secretary also has asked Special Operations Command to take the lead in some anti-terrorism operations. That is a change from the usual arrangement of having a regional command, such as the Middle East-oriented Central Command, take the lead.

Special Operations Command is so secretive that its Defense Department Web site offers nothing about it except a likeness of its insignia (adapted from one designed by William Donovan's Office of Strategic Services, a forerunner of the CIA) and information on how defense contractors can submit proposals.

The covert side of the military's special operations force resides in a sub-command, known as the Joint Special Operations Command. Based at Fort Bragg, N.C., it reportedly has command of the Special Forces Operational Detachment Delta, or Delta Force, a secretive counterterrorism unit.

William Arkin, a private military and intelligence expert who has written about the Pentagon's efforts to expand covert capabilities, says Rumsfeld is building up "an elite secret army" and that this emphasis on covert action reflects Pentagon frustrations with the performance of the CIA and other intelligence agencies.

"Insulated from outside pressures, armed with matchless weapons and technology, trained to operate below the shadow line, the Pentagon's black world of classified operations holds out the hope of swift, decisive action" in the war on terror, Arkin wrote recently in the Los Angeles Times.

This approach fits with Rumsfeld's emphasis on pre-empting future terrorist attacks, in the wake of Sept. 11, 2001, rather than relying on the military's traditional approach of organizing forces to defend against or to deter attacks.

In fact the word "pre-emptive" is in the name given a proposed new counter-terrorism organization. The "Proactive Preemptive Operations Group" would be comprised of about 100 people with experience in covert activities, intelligence gathering, computer network attacks and other highly specialized skills.

The group would be overseen by the White House's deputy national security adviser for combatting terrorism, John A. Gordon, and it would carry out missions coordinated by the secretary of defense or the CIA director.

The idea of creating this group was proposed in August by the Defense Science Board, which advises the secretary of defense. Another recommendation is that the CIA and Pentagon increase emphasis on counterterrorism covert action and develop a way to "enable deep penetration of adversaries."

"The proposal is the latest sign of a new assertiveness by the Defense Department in intelligence matters, and an indication that the cutting edge of intelligence reform is not to be found in Congress but behind closed doors in the Pentagon," Steven Aftergood of the Federation of American Scientists wrote in an analysis of the plan.

The study also called for expanding the Pentagon's human intelligence, or humint, services abroad and ensuring a role for special operations forces.